This releases a greater volume of water and is intended for solid waste.
The stronger flush helps move waste through the toilet’s trapway and drainage system.
So, in simple terms:
Small/reduced button → liquid waste
Large/full button → solid waste
However, the exact button arrangement can vary between toilet models.
That’s important.
Not every toilet uses the same visual design.
Some manufacturers put the reduced flush on the smaller button.
Others use different symbols or button arrangements.
EPA has even noted that people can have difficulty identifying which button activates the reduced flush on some toilet designs. (EPA NERL)
So if you’re unsure, check the manufacturer’s instructions.
Why Not Just Use the Big Button Every Time?
This is where the design becomes interesting.
A toilet needs water to transport waste.
But more water isn’t automatically better for every situation.
If a small amount of liquid waste can be removed effectively with a reduced flush, using a full flush unnecessarily wastes additional water.
That is the basic environmental idea behind dual flushing.
The EPA’s WaterSense program says choosing a reduced flush for liquid waste can save water compared with using a larger flush every time. (US EPA)
Think about it like this.
You wouldn’t fill a huge bucket every time you needed a glass of water.
You would use an amount appropriate to the task.
A dual-flush toilet applies a similar principle to flushing.
Where Did the Idea Come From?
The concept of giving people a choice between different flush volumes developed as part of efforts to reduce water consumption.
Traditional toilets generally offered one flush volume.
Whether you used the toilet for liquid waste or solid waste, the mechanism released essentially the same amount of water.
Dual-flush toilets introduced another possibility.
Instead of asking:
“How much water does this toilet always use?”
the system asks:
“How much water is appropriate for this particular flush?”
That small change in design can make water efficiency part of everyday behavior.
It’s Not Two Toilets in One
One common misunderstanding is that the two buttons somehow operate two separate systems.
Usually, they are controlling different modes of the same toilet flushing mechanism.
Inside the tank, the buttons are connected to the flush valve or related mechanism.
Pressing one button activates one flush volume.
Pressing the other activates another.
The internal mechanism varies by manufacturer.
